Evaluating Geologic Hazards associated with faulting on the Olympic Peninsula

Morgan Zeliff

Whitman College, Walla Walla, WA 99362

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The Olympic Peninsula, situated just west of Washington’s most populous region, was created and is still being shaped by several complex geologic processes. These geologic processes broadly include tectonics (currently in the form of earthquakes, which also produce the now widely known hazards of tsunamis), mass-wasting, glacial processes and fluvial processes. All of these processes present a potential hazard to the population living in vicinity to this region. The tectonics of the region is possibly the least understood process. In order to have a more complete and better understanding of the regions tectonic hazard it is necessary to investigate the effects of events from the past so that proper precautions can be taken in the present and future.

The opportunity arose for me to join a team of professional geologists in the excavation of trench across of what has been assumed to be a Holocene in age fault scarp along the eastern side of the Olympic Peninsula. This project prompted me, in collaboration with another geology student, my professor Bob Carson and several other professional geologists, to investigate the area, the scarp and other nearby geologic related features, and to combine what data I collected with the information deciphered from the trench. I propose to focus my thesis on a gouge-core study I conducted while also helping out with the trenching activities. I will be investigating possible evidence for amount of displacement along the scarp by examining depths to buried sediment layers from a cross section bisecting the scarp. This data in combination with the evidence from the trench, a magnetic survey and another gouge core study will hopefully come together to produce a paper that will demonstrate the amount of the geologic hazard in the area. Also, I may be able to use the data to put the fault into more of a regional context, helping to fit together the complex puzzle of the active tectonics in the territory as a whole.